1. Technical Field
The present invention relates to a neutron moderator mainly used for neutron capture therapy, a method for manufacturing the neutron moderator, and a method for manufacturing a magnesium fluoride sintered compact that is optimal for a neutron moderator.
2. Description of the Related Art
Various materials have been studied for a neutron moderator that is used for selective treatment of cancer such as boron neutron capture therapy. Examples of the materials include lithium fluoride, aluminum fluoride, and magnesium fluoride. Of these materials, magnesium fluoride is specifically known as an optimal material for a neutron moderator due to its excellent function in moderating the energy of neutron beams to 10 key or lower.
The technique described in Japanese Patent Application Laid-open No. 2004-233168 (JP-A-2004-233168) mentioned above uses lithium fluoride for a neutron moderator. Lithium used in the technique described in JP-A-2004-233168, however, presents an issue of manufacturing cost, because Lithium is one of rare metals.
In view of the above issue, “Optimizing the OSU-ABNS Base Moderator Assembly Materials for BNCT B. Khorsandia*, T. E. Blue a Nuclear Engineering Program, The Ohio State University, Columbus, Ohio 43210, USA” describes that magnesium fluoride has an excellent neutron moderating function for moderating the energy of neutrons in the range of 10 keV or lower. In addition, “Accelerator-Based source of epithermal neutrons for neutron capture therapy. Kononov O E, Kononov V N, Solov' EV A N, Bokhovko M V At Energy Vol. 97 No. 3, PP 626-631” describes a moderator combining magnesium fluoride and polytetrafluoroethylene.
In order to manufacture a neutron moderator only with magnesium fluoride and without using polytetrafluoroethylene to have a good neutron moderating performance, it is appropriate to process magnesium fluoride into a sintered compact. For a neutron moderator, a magnesium fluoride sintered compact is preferably made into a predetermined size, to be free from cracks and chipping and to have high relative density.
The present invention has been made in view of the above considerations, and is directed to providing a method for manufacturing a magnesium fluoride sintered compact to be free from cracks and chipping and to have high relative density, and also providing a method for manufacturing a neutron moderator, and the neutron moderator.